Task-lit cabinet

ABSTRACT

Methods, apparatuses, and products passively generate electrical energy from waste heat. Electronic components in cabinets generate waste heat that is used to illuminate an interior of a cabinet. A thermovoltaic semiconductor detects a temperature differential between a pair of terminals installed in the cabinet. The thermovoltaic semiconductor generates a low voltage output in response to the temperature differential. A power supply receives the low voltage output and produces a higher voltage for low-wattage light sources installed in the cabinet.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/112,215 filed May 20, 2011 and since issued as U.S. Pat. No.9,076,893, which is incorporated herein by reference in its entirety.

BACKGROUND

Exemplary embodiments generally relate to power plants, to prime-moverdynamo plants, and to electrical systems and devices and, moreparticularly, to motive fluid energized by externally applied heat, tofluid-current motors, to ventilation, to electronic cabinets, and toelectrical systems and devices.

Data centers generate waste heat. Data centers house racks of electroniccomponents in cabinets. Because the electronic components generate wasteheat, the waste heat could be reused.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The features, aspects, and advantages of the exemplary embodiments arebetter understood when the following Detailed Description is read withreference to the accompanying drawings, wherein:

FIG. 1 is a simplified schematic illustrating an environment in whichexemplary embodiments may be implemented;

FIG. 2 illustrates passive electrical generation, according to exemplaryembodiments;

FIG. 3 is a more detailed schematic illustrating a cabinet, according toexemplary embodiments;

FIG. 4 is a block diagram illustrating a power supply, according toexemplary embodiments;

FIGS. 5 and 6 are schematics illustrating a bus cable, according toexemplary embodiments;

FIG. 7 is a schematic illustrating a switch, according to exemplaryembodiments;

FIG. 8 is a schematic illustrating a passive turbine, according toexemplary embodiments;

FIGS. 9 & 10 are more block diagrams further illustrating the powersupply, according to exemplary embodiments; and

FIG. 11 is a flowchart illustrating a method of passively generatingelectrical energy from waste heat, according to exemplary embodiments.

DETAILED DESCRIPTION

The exemplary embodiments will now be described more fully hereinafterwith reference to the accompanying drawings. The exemplary embodimentsmay, however, be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein. Theseembodiments are provided so that this disclosure will be thorough andcomplete and will fully convey the exemplary embodiments to those ofordinary skill in the art. Moreover, all statements herein recitingembodiments, as well as specific examples thereof, are intended toencompass both structural and functional equivalents thereof.Additionally, it is intended that such equivalents include bothcurrently known equivalents as well as equivalents developed in thefuture (i.e., any elements developed that perform the same function,regardless of structure).

Thus, for example, it will be appreciated by those of ordinary skill inthe art that the diagrams, schematics, illustrations, and the likerepresent conceptual views or processes illustrating the exemplaryembodiments. The functions of the various elements shown in the figuresmay be provided through the use of dedicated hardware as well ashardware capable of executing associated software. Those of ordinaryskill in the art further understand that the exemplary hardware,software, processes, methods, and/or operating systems described hereinare for illustrative purposes and, thus, are not intended to be limitedto any particular named manufacturer.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless expressly stated otherwise. Itwill be further understood that the terms “includes,” “comprises,”“including,” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof. It will be understood thatwhen an element is referred to as being “connected” or “coupled” toanother element, it can be directly connected or coupled to the otherelement or intervening elements may be present. Furthermore, “connected”or “coupled” as used herein may include wirelessly connected or coupled.As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items.

It will also be understood that, although the terms first, second, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first device could be termed asecond device, and, similarly, a second device could be termed a firstdevice without departing from the teachings of the disclosure.

FIGS. 1 and 2 are simplified schematics illustrating an environment inwhich exemplary embodiments may be implemented. FIG. 1 illustrates adata center 20 housing one or more cabinets 22. While only a fewcabinets 22 are illustrated, the data center 20 may house many cabinets22, such as fifty (50) or even more cabinets. Each cabinet 22 houses avertical or horizontal rack 24. Various electronic components 26 areinstalled in each rack 24. The electronic components 26 may includeservers, routers, storage devices, computers, and/or any other equipmentneeded or desired. Regardless, the electronic components 26 generatewaste heat 28 during their operation, as is well-known.

FIG. 2 illustrates passive electrical generation, according to exemplaryembodiments. Here, exemplary embodiments recover energy contained in thewaste heat 28. The cabinet 22 houses a power supply 40. The power supply40, however, is passive in that no electrical energy from an electricalgrid is fed or input to the power supply 40. The power supply 40,instead, generates electrical power from the waste heat 28. The powersupply 40, for example, receives electrical power produced by athermovoltaic semiconductor 42. The thermovoltaic semiconductor 42generates electrical energy from the waste heat 28 (as later paragraphswill explain). Similarly, the power supply 40 receives electrical powerproduced by a passive turbine 44. The passive turbine 44 is rotated by athermal draft produced by the waste heat 28 (as later paragraphs willalso explain). The turbine 44 mechanically couples to a generator 46,and the generator 46 converts mechanical energy into electrical energy.The power supply 40 is electrically coupled to the generator 46 toreceive electrical power generated from the thermal draft produced bythe waste heat 28. The electrical energy produced by the thermovoltaicsemiconductor 42 and/or the generator 46 is fed or input to the powersupply 40. The power supply 40 may then process or condition theelectrical energy for use.

Exemplary embodiments provide interior lighting of the cabinet 22.Because the waste heat 28 is used to generate electrical energy, theelectrical energy may be used to light an interior 50 of the cabinet 22.The cabinet 22 may include one or more light sources 52. Each lightsource 52 receives electrical power from the power supply 40 and outputsvisible light to the interior 50 of the cabinet 22. While the lightsources 52 may include incandescent filaments, halogen elements, andother conventional light bulbs, the light sources 52 are preferablylight emitting diodes (or “LEDs”). Light emitting diodes provide ampleillumination and, yet, operate at low voltages. Should the electroniccomponents 26 in the cabinet 22 need service, exemplary embodiments thuspermit illuminating the interior 50 of the cabinet 22 without electricalpower from the electrical grid. Exemplary embodiments thus recycle theexisting waste heat 28 into free lighting while reducing overheadlighting and energy costs.

FIG. 3 is a more detailed schematic illustrating the cabinet 22,according to exemplary embodiments. Here the thermovoltaic semiconductor42 detects a temperature differential 60 between a pair 62 of terminals.The thermovoltaic semiconductor 42 then generates a low voltage output64 in response to the temperature differential 60. A first terminal 66of the pair 62 of terminals, for example, may be installed in orproximate a cooler portion 68 of the cabinet 22. A second terminal 70 ofthe pair 62 of terminals may be installed in or proximate a warmerportion 72 of the cabinet 22. The thermovoltaic semiconductor 42 thengenerates the low voltage output 64 in response to the temperaturedifferential 60 between the cooler portion 68 of the cabinet 22 and thewarmer portion 72 of the cabinet 22.

A maximum temperature differential is desired. Because the thermovoltaicsemiconductor 42 generates the low voltage output 64 in response to thetemperature differential 60, a maximum temperature differentialgenerates a maximum electrical power. Temperature testing or temperatureprobing may thus be used to determine a coolest location within thecabinet 22 and a hottest location within the cabinet 22. The coolerportion 68 of the cabinet 22 may thus be any location or region withinthe cabinet 22 having a lowest operating temperature, while the warmerportion 72 of the cabinet 22 may thus be any location or region withinthe cabinet 22 having a hottest operating temperature. FIG. 2, forexample, illustrates the first terminal 66 located at or proximate anupper area 74 of a front side 76 of the cabinet 22. The front side 76 ofthe cabinet 22 may be, or contain, an access door 78 that allows accessto the electrical components (illustrated as reference numeral 26 inFIG. 1). Testing has shown that the upper area 74 of the front side 76may be the coolest location within the cabinet 22. FIG. 2 alsoillustrates the second terminal 70 installed in or proximate the upperarea 74 of a back side 80 of the cabinet 22, where testing reveals thehottest location.

The thermovoltaic semiconductor 42 generates electrical energy and powerfrom the waste heat 28. The pair 62 of terminals detects the temperaturedifferential 60 between the first terminal 66 and the second terminal70. The thermovoltaic semiconductor 42 is a semiconductor material thatgenerates the low voltage output 64 in response to the temperaturedifferential 60. The thermovoltaic semiconductor 42 thus convertsthermal energy into an electrical potential.

FIG. 4 is a block diagram illustrating the power supply 40, according toexemplary embodiments. Here the power supply 40 receives electricalpower generated by the thermovoltaic semiconductor 42 and/or by thepassive turbine 44. The power supply 40, for example, has a first input90 connected to an output 92 of the thermovoltaic semiconductor 42. Thepower supply 40 also has a second input 94 connected to an output 96 ofthe passive turbine 44. The power supply 40 may also has a connection 98to electrical ground 100. The power supply 40 thus receives electricalpower that has been passively generated by the thermovoltaicsemiconductor 42 and/or by the passive turbine 44. The power supply 40produces an output voltage 102 that drives a load 104. Here, though, theload 104 is a series or parallel arrangement of the light sources 52(such as light emitting diodes) for illuminating the interior of thecabinet.

The power supply 40 may include an upconverter circuit 110. Theupconverter circuit 110 boosts, or steps up, voltages available from thethermovoltaic semiconductor 42 and/or by the passive turbine 44. Theupconverter circuit 110, in other words, converts the low voltage output64 (generated by the thermovoltaic semiconductor 42) to a higher voltage112. The upconverter circuit 110, likewise, converts any low voltagegenerated by the passive turbine 44 to the higher voltage 112. The powersupply 40, for example, may receive a 1 Volt direct current (DC) inputand produce the higher voltage of 12 Volts DC. Even though theupconverter circuit 110 boosts low voltages to higher voltages, totalpower remains the same. That is, conservation of energy requires thatpower input to the upconverter circuit 110 must be equal to power outputfrom the upconverter circuit 110. So, even though low voltages areboosted, current may be reduced.

The power supply 40 may also include a capacitor storage circuit 114.The capacitor storage circuit 114 utilizes one or more capacitors tostore electrical power transferred by the upconverter circuit 110 (aslater paragraphs will explain).

The power supply 40 may also include a voltage regulator circuit 116.The voltage regulator circuit 116 controls the output voltage 112(and/or an output current) to a specific value. That is, the outputvoltage 112 is held nearly constant despite variations in electricalpower generated by the thermovoltaic semiconductor 42 and/or the passiveturbine 44. Light emitting diodes, for example, may require a relativelyconstant voltage (e.g., 3 Volts DC) for operation. The voltage regulatorcircuit 116 helps ensure the power supply provide adequate voltage topower light emitting diodes.

The power supply 40 may also include means for storing electricalenergy. When electrical power is passively generated by thethermovoltaic semiconductor 42 and/or by the passive turbine 44, theelectrical power may be stored for later retrieval and use. A battery118, for example, may be used to store electrical power passivelygenerated by the thermovoltaic semiconductor 42 and/or by the passiveturbine 44. The battery 118 may have any chemical and/or metallurgicalconstruction for storing electrical energy. Because batteries are wellknown to those of ordinary skill in the art, a further description ofthe battery 118 is not necessary.

FIGS. 5 and 6 are schematics illustrating a bus cable 130, according toexemplary embodiments. The bus cable 130 has a first connection 132 toan output terminal 134 of the power supply 40. The bus cable 130 has asecond connection 136 to the electrical ground 100. The bus cable 130receives the output voltage (illustrated as reference numeral 102 inFIG. 4) produced by the power supply 40 and distributes the outputvoltage 102 along the bus cable 130. Each light emitting diode 52 maythus connect to the bus cable 130 to receive the output voltage 102 forilluminating the cabinet 22. Each light emitting diode 52 is preferablyan inexpensive, but efficient, strip 138 that adhesively adheres 140 toan interior side wall 142 of the cabinet 22. The bus cable 130 may alsoadhesively adhere to the interior side wall 142 of the cabinet 22. Aninexpensive adhesive, double-sided tape, or even a hook-and-loopfastener may be used to quickly and easily secure the bus cable 130 andeach light emitting diode 52 to the interior side wall 142 of thecabinet 22. The bus cable 130 and each light emitting diode 52, however,may alternatively be secured by mechanical fasteners.

As FIG. 6 illustrates, the bus cable 130 may include a connection 150 toother cabinets. Because the data center 20 may have many cabinetsstoring the electrical components, the cabinets may be connected, ordaisy-chained, together. A cable 152 may connect a first cabinet 154 toa neighboring second cabinet 156. The connection 150 thus permits thefirst cabinet 154 to supply electrical power to the neighboring secondcabinet 156. The connection 150, likewise, also permits the firstcabinet 154 to consume electrical power from the neighboring secondcabinet 156. As FIG. 6 illustrates, the bus cable 130 may physicallyconnect to a second bus cable 158 installed or operating in theneighboring second cabinet 156. The connection 150 may this be amale-to-female connector that establishes a series or parallelconnection to the second bus cable 158. All the cabinets in the datacenter 20 may thus be interconnected to provide, or draw, electricalpower in times of electrical need. For example, should the power supply40 be unable to provide enough electrical power to illuminate the firstcabinet 154, then a neighboring power supply 160 in the second cabinet156 may provide electrical power to illuminate the first cabinet 154.

FIG. 7 is a schematic illustrating a switch 170, according to exemplaryembodiments. Here the power supply 40 may electrically interface with,or connect to, the switch 170 to control application of the outputvoltage 102 to the bus cable 130. The switch 170, for example, allowspersonnel to illuminate the interior 50 of the cabinet 22. When theswitch is open (or “off”), the output voltage 102 from the power supply40 is not applied to the bus cable 130. When the switch is closed,though, the switch 170 is “on” and the output voltage 102 from the powersupply 40 is applied to the bus cable 130. The switch 170, for example,is preferably actuated by the access door 78 of the cabinet 22. When theaccess door 78 is open, the switch 170 closes to illuminate the interior50 of the cabinet 22. When the access door 78 is closed, the switch 170opens and removes illumination. The switch 170 may thus create aconnection between the power supply 40 and the bus cable 130 to produceillumination. The switch 170, however, may be any switch with anyconfiguration or mounting (such as a wall switch or toggle switch).

FIG. 8 is a schematic illustrating the passive turbine 44, according toexemplary embodiments. The passive turbine 44 has a rotor assembly 180.As the electrical components (illustrated as reference numeral 22 inFIG. 1) generate the waste heat 28, the waste heat 28 produces a thermaldraft 182. The cabinet 22 may have an exit port 184 through which thethermal draft 182 convects or flows. The passive turbine 44 is placed inthe flow of the thermal draft 182, such that the thermal draft 182drives one or more blades of the rotor assembly 180. The rotor assembly180 turns or drives the generator 46. The generator 46 convertsmechanical energy of the rotor assembly 180 into electrical energy(either alternating current or direct current, as is known). Theelectrical power generated by the passive turbine 44 is fed to, orreceived by, the power supply 40. The power supply 40 produces theoutput voltage 102 that drives the load 104 (such as the light sources52, as earlier paragraphs explained).

FIG. 9 is another block diagram further illustrating the power supply40, according to exemplary embodiments. Here the power supply 40 mayhave a processor 200, application specific integrated circuit (ASIC), orother component that executes an energy management application 202stored in a memory 204. The energy application 202 may cause theprocessor 200 to receive the low voltage output 64 produced by thethermovoltaic semiconductor 42 (in response to the temperaturedifferential 60). The processor 200 may also receive a generator outputvoltage 206 generated by the passive turbine 44. The energy application202 may cause the processor 200 to logically sum these voltages toproduce a summed voltage 208. The energy application 202 may then causethe processor 200 to send the summed voltage 208 to the upconvertercircuit 110. The upconverter circuit 110 boosts, converts, or steps upthe summed voltage 208 to produce a boosted voltage 210. The energyapplication 202 may then cause the processor 200 to instruct the voltageregulator circuit 116 to condition the boosted voltage 210 to the nearlyconstant output voltage 102. When the output voltage 102 is immediatelyneeded (such as when illumination is needed), the energy application 202may then cause the processor 200 to send, or couple, the output voltage102 to the bus cable 130. When some or all of the output voltage 102 isnot needed, the energy application 202 may then cause the processor 200to send, or couple, the output voltage 102 to the battery 118. Theenergy application 202 may even cause the processor 200 to perform moreenergy management functions, such as managing the electrical powerstored in the battery 118. The energy application 202 may receive abattery voltage 212 of the battery 118, and the processor 200 activelymanages the battery voltage 212 to maintain a minimum value 214.

The power supply 40 may also have a network interface 220 to acommunications network 222. Because the power supply 40 may beprocessor-controlled, the power supply 40 may be remotely monitored andcommanded. One or more commands 224 may be addressed to the power supply40, and these commands 224 instruct the processor 200 and/or the energymanagement application 202 to perform specified functions. The powersupply 40, for example may be remotely commanded to turn “on” or “off”illumination. The power supply 40 may be remotely commanded to reportthe electrical power being passively generated by the thermovoltaicsemiconductor 42 and/or by the passive turbine 44. The power supply 40may be remotely commanded to report the battery voltage 212 of thebattery 118 or power being consumed during illumination of the cabinet22. The energy application 202 may be remotely commanded to reporttemperatures 226 inside the cabinet 22 (such as the temperaturedifferential 60 between the first terminal 66 and the second terminal70, as illustrated in FIG. 2). The power supply 40 may thus send anacknowledgment 228 of each command 224 and/or a response 230 to anycommand 230.

Exemplary embodiments may be applied regardless of networkingenvironment. The communications network 222 may be a cable networkoperating in the radio-frequency domain and/or the Internet Protocol(IP) domain. The communications network 222, however, may also include adistributed computing network, such as the Internet (sometimesalternatively known as the “World Wide Web”), an intranet, a local-areanetwork (LAN), and/or a wide-area network (WAN). The communicationsnetwork 222 may include coaxial cables, copper wires, fiber optic lines,and/or hybrid-coaxial lines. The communications network 222 may eveninclude wireless portions utilizing any portion of the electromagneticspectrum and any signaling standard (such as the I.E.E.E. 802 family ofstandards, GSM/CDMA/TDMA or any cellular standard, and/or the ISM band).The communications network 222 may even include powerline portions, inwhich signals are communicated via electrical wiring. The conceptsdescribed herein may be applied to any wireless/wireline communicationsnetwork, regardless of physical componentry, physical configuration, orcommunications standard(s).

FIG. 10 is another block diagram further illustrating the power supply40, according to exemplary embodiments. Here, though, the upconvertercircuit 110 is schematically illustrated to show its possible circuitcomponents. The upconverter circuit 110 may have an inductor (“L”). Theinductor L resists changes in current (“I_(L)”). As the inductor ischarged, the inductor absorbs electrical energy. As the inductor isdischarged, though, the inductor acts as an energy source to produce avoltage across its terminals. The voltage produced across the inductorterminals (during the discharge phase) is related to a rate of change ofthe current I_(L) flowing through the conductor. When switch S isclosed, the current I_(L) increases through the inductor L. When theswitch S is open, though, the current I_(L) must flow through diode Dand split through capacitor C and load R. The opening of the switch Sresults in transferring the energy accumulated in the inductor L intothe capacitor C. The capacitor C thus stores the electrical energyproduced by the inductor L (resulting in the capacitor storage circuit114, illustrated in FIGS. 4 & 9).

FIG. 11 is a flowchart illustrating a method of passively generatingelectrical energy from the waste heat 28, according to exemplaryembodiments. Electrical energy is generated from the waste heat 28(Block 250). (The waste heat 28, for example, may create a heatdifferential between a hot aisle and a cold aisle of the data center20.) Electrical energy is may also be generated from the thermal draft182 created by the waste heat 28 (Block 252). The electrical energy issummed (Block 254), boosted to a higher voltage (Block 256), and storedin the battery 118 (Block 258). When task lighting in the cabinet 22 isneeded (Block 260), the electrical energy stored in the battery 118 isdirected to the light sources 52 in the cabinet 22 (Block 262).

Exemplary embodiments may be physically embodied on or in acomputer-readable storage medium. This computer-readable medium mayinclude CD-ROM, DVD, tape, cassette, floppy disk, memory card, andlarge-capacity disks. This computer-readable medium, or media, could bedistributed to end-subscribers, licensees, and assignees. A computerprogram product comprises processor-executable instructions forpassively generating electrical energy from the waste heat 28 in thecabinet 22, as the above paragraphs explained.

While the exemplary embodiments have been described with respect tovarious features, aspects, and embodiments, those skilled and unskilledin the art will recognize the exemplary embodiments are not so limited.Other variations, modifications, and alternative embodiments may be madewithout departing from the spirit and scope of the exemplaryembodiments.

The invention claimed is:
 1. An apparatus, comprising: a cabinet forhousing a rack of electronic components, the cabinet having ports toconvect waste heat from an interior of the cabinet, the waste heatproduced by the electronic components housed within the cabinet; athermovoltaic semiconductor having a pair of terminals, a first terminalof the pair of terminals installed proximate an upper frontal area ofthe cabinet, a second terminal of the pair of terminals installedproximate an exit port of the ports in an opposite upper backside areaof the cabinet, the thermovoltaic semiconductor passively generatingelectrical power in response to a temperature differential between thepair of terminals; selectively connecting an end of a bus cable to anoutput terminal of the thermovoltaic semiconductor, the bus cabledistributing the electrical power to interior lighting that illuminatesan interior of the cabinet; and series connecting another end of the buscable to another bus cable in a neighboring cabinet, the bus cable andthe another bus cable daisy chained together to electrically distributethe electrical power passively generated by the thermovoltaicsemiconductor to the neighboring cabinet.
 2. The apparatus of claim 1,further comprising a light emitting diode connected to the bus cable toreceive the electrical power and to produce the interior lightingilluminating the interior of the cabinet.
 3. The apparatus of claim 1,further comprising a light emitting diode adhesively adhered to aninterior sidewall of the cabinet, the light emitting diode connected tothe bus cable to receive the electrical power and to produce theinterior lighting illuminating the interior of the cabinet.
 4. Theapparatus of claim 1, further comprising a switch connected between theoutput terminal of the thermovoltaic semiconductor and the end of thebus cable.
 5. The apparatus of claim 4, wherein the switch electricallycloses when a door in the cabinet is opened, the switch creating anelectrical connection between the output terminal of the thermovoltaicsemiconductor and the end of the bus cable.
 6. The apparatus of claim 4,wherein the switch electrically opens when a door in the cabinet isclosed.
 7. A method, comprising: convecting waste heat from a cabinet,the waste heat produced by electronic components racked within thecabinet; passively generating electrical power by a thermovoltaicsemiconductor, the thermovoltaic semiconductor having a first terminalinstalled proximate an upper frontal area of the cabinet, thethermovoltaic semiconductor having a second terminal installed proximatean exit port in an opposite upper backside area of the cabinet, thethermovoltaic semiconductor passively generating the electrical power inresponse to a temperature differential between the first terminal andthe second terminal caused by the waste heat produced by the electroniccomponents in the cabinet; selectively connecting an end of a bus cableto an output terminal of the thermovoltaic semiconductor, the bus cabledistributing the electrical power to interior lighting that illuminatesan interior of the cabinet; and series connecting another end of the buscable to another bus cable in a neighboring cabinet racking additionalelectronic components, the bus cable and the another bus cable daisychained together to electrically distribute the electrical powerpassively generated by the thermovoltaic semiconductor to the additionalelectronic components racked in the neighboring cabinet.
 8. The methodof claim 7, further comprising connecting a light emitting diode to thebus cable to receive the electrical power and to produce the interiorlighting illuminating the interior of the cabinet.
 9. The method ofclaim 8, further comprising adhesively adhering the light emitting diodeto an interior sidewall of the cabinet.
 10. The method of claim 7,further comprising connecting a switch between the output terminal ofthe thermovoltaic semiconductor and the end of the bus cable.
 11. Themethod of claim 10, further comprising closing the switch when a door inthe cabinet is opened, the switch creating an electrical connectionbetween the output terminal of the thermovoltaic semiconductor and theend of the bus cable.
 12. The method of claim 10, further comprisingopening the switch when a door in the cabinet is closed.
 13. The methodof claim 7, further comprising storing the electrical power passivelygenerated by the thermovoltaic semiconductor in a battery housed withinthe cabinet.